Preparation of alkyl sulfides



United States Patent 3,376,348 PREPARATION OF ALKYL SULFIDES George B.Stratton, Lewiston, N.Y., assignor to Hooker Chemical Corporation,Niagara Falls, N.Y., a corporation of New York No Drawing. Filed Feb.12, 1964, Ser. No. 344,239 11 Claims. (Cl. 260-609) This inventionrelates to a novel process for preparing organic sulfides. Moreparticularly, it is of the reaction of an olefin with a tertiarymercaptan in the presence of an azo catalyst.

There are numerous methods for preparing sulfides, such as by the freeradical catalyzed abnormal addition of a mercaptan to an olefin in thepresence of a peroxide or ultraviolet light. However, these reactionsare difiicult and expensive to accomplish. They result in low yields ofa sulfide which is impure, and, the reaction is, also, very dangerous toeffect, as high pressures have to be employed.

In accordance with the present invention there is provided a process forthe preparation of an organic sulfide which comprises reacting an olefinwith a tertiary mercaptan in the presence of an azo catalyst, as will bemore fully described herein. The reaction occurring can be illustratedby the following equation which is not intended to be limiting.

wherein, the substituents R, R R and R are alkyl radicals.

Among the R, R R and R alkyl substituents are, for example, alkylradicals containing from 1 to about 20 carbon atoms, and preferably from1 to about carbon atoms, such as, methyl, ethyl, propyl, isopropyl,butyl, secondary butyl, tertiary butyl, pentyl, heptyl, octyl, decyl,pentadecyl, heptadecyl, eicosyl, and the like, said alkyl group beingdefined as a monovalent radical derived from an aliphatic hydrocarbon bythe removal of one hydrogen atom. The R, R R and R substituents may bethe same or ditferent.

The azo catalyst employed in the process of this invention includesthose compounds containing the grouping N=N, said catalyst possessingfrom 6 to about carbon atoms and preferably from 8 to about 14 carbonatoms. Illustrative examples of azo catalysts includealpha(carbamylazo)-alpha-methyl enanthonitrile, alpha-(carbamylazo)isobutyramide, hexyl alpha(carbamylazo)- alpha,gamma-dimethylvalerate, alpha,alpha-azodiisobutyronitrile,alpha,alpha'azobis-(alpha,gamma-dimethylvaleronitrile),alpha,alpha'-azobis-(alpha-ethylbutyronitrile), a1pha,alpha azobis(alphacy-clohexylpropionitrile),alpha,alpha'-azobis(alpha,gamma-dimethylcapronitrile),l,1-azodicyclohexanecarbonitrile, l,l'-azodicycloheptanecarbonitrile. Amore detailed list of these types of catalyst appears in US. Patent2,551,813. The preferred catalyst is alpha,alpha-azodiisobutyronitrile.

Olefins which may be employed in the practice of the present inventioninclude those olefins having a carbon chain length of from 2 to about 20carbon atoms, and preferably of 2 to about 16 carbon atoms, such as,ethene, butene, pentene, octene, decene, dodecene, tetradecene,hexadecene, octene-l, dodecene-l, octadecene, eicosene, and the like,for example. Mixtures of olefins can, also, be utilized, if desired.

The mercaptan which reacts with the olefin will preferably be a tertiarymercaptan. Some commercially available tertiary mercaptans for thistechnique include tertiary butyl mercaptan, tertiary isopropylmercaptan,tertiary nonyl mercaptan, tertiary dodecylmercaptan and mixed tertiarymercaptans.

In general, the azo catalyst is present in the reaction system inamounts from 0.5 to 10 percent by weight based upon the weight ofolefin, and preferably of from 1 to about 3 percent by weight. However,smaller amounts, for example, as low as .1 percent or less, are oftenefiective and can be employed, if desired. Amounts about 10 percent ormore may be used, 'but the relative expense of such large amounts ofcatalyst and the lack of significantly improved results generallyprecludes their use.

The ratio of olefin to mercaptan is in the range of from 0.2 to about 20moles of olefin to 1 mole of mercaptan, with a preferred range being 1to 10 and the most preferred ratio being about 1 mole olefin to 1 molemercaptan.

Pressures are generally about atmospheric, but super or subatmosphericpressures may, also, be employed to effect the reaction.

The temperature at which the reaction is efiected depends upon thecatalyst and olefin being utilized, as well as on the reaction ratedesired. Although temperatures within the range of from 40 degrees todegrees centigrade have been illustrated in the examples, temperaturesof from 30 degrees to 200 degrees centigrade can be used, depending uponthe catalyst and the reaction rate desired. The reaction rate is high attemperatures at which the particular catalyst employed is considered todecompose rapidly into the fragments which initiate the reaction. With agiven catalyst, an increase in temperature generally results in a higherreaction rate. A plurality of azo catalysts may be employed to lengthenthe active temperature range, if desired. Generally, the reaction takesplace in approximately 30 minutes to around 15 hours, although thespecific time employed may be varied.

In a preferred embodiment, the process of the present invention isillustrated by the following specific equation:

Sulfides which can be produced by the process of this invention include,for example, the following:

In order that those skilled in the art may better understand the presentinvention and the manner in which it may be practiced, the followingillustrative examples are g1ven.

In the specification, examples and claims, parts are by weight andtemperatures are in degrees Centigrade, unless otherwise stated.

EXAMPLE 1 Ten moles of a-octene (C H and 11 moles of tertiarybutyl-mercaptan were heated together in the presence of 5 grams ofazobisisobutyronitrile (alpha,alpha-azodiisobutyronitrile) for a periodof about 30 hours and at a temperature of 55-60 degrees Centigrade. Theproduct was recovered by distillation and the recovered olefin isrecycled, used again in the next such reaction. The n-octyl tertiarybutylsulfide product was obtained in a yield of 97.5 percent.

3 In a similar manner to the above and at substantially the sameproportion, a-decene is employed in the place of octene resulting inn-decane tertiary butyl sulfide.

EXAMPLE 2 One mole of a mixture of a-olefins containing 7 to 9 carbonsand 1.1 moles of tertiary butyl mercaptan were reacted together in thepresence of one-half gram of azobisisobutyronitrile at a temperature of60 degrees centigrade for a period of 35 hours. The product wasrecovered by distillation and the recovered olefin was recycled backinto the next reaction system. The mixed alkyl tertiary butyl sulfide isobtained in 87 percent yield on recycling.

In a similar manner to the above and at substantially the sameproportion, a mixture of tat-olefins containing 11-15 carbons isemployed in the place of the olefin mixture containing 7 to 9 carbonatoms, resulting in normal tertiary butyl sulfides containing from 15 to19 carbon atoms.

EXAMPLES 3-10 The procedure of Example 1 is repeated and the followingreactions are efiected to produce the products shown with tertiary butylmercaptan 4. A process in accordance with claim 1 wherein a mixture ofolefins containing from 11 to 15 carbon atoms is utilized.

5. A process in accordance with claim 1 wherein the reaction is effectedat a temperature of from 40 degrees centigrade to 140 degreescentigrade.

6. A process in accordance With claim 5 wherein the reaction is effectedat a temperature of from '50 degrees centigrade to 70 degreescentigrade.

7. A process according to claim 5 wherein the azo catalyst is selectedfrom the group consisting of alpha (carbamylazo)alpha-methylenanthonitrile, alpha(carbamylazo)isobutyramide, hexylalpha(carbamylazo)-alpha, gamma-dimethylvalerate, alpha,alpha'-azodiisobutyronitrile, alpha, alpha-azobis-(a1pha,gamma-dimethylvaleronitrile), alpha,a1pha'-azobis-(alpha-ethylbutyronitrile), alpha,alpha-azobis(alpha-cyclohexylpropinonitrile), alpha, alpha-azobis(alpha,gamma-dirnethylcapronitrile), 1,1-azodicyclohexanecarbonitrile,1,1-azdicycloheptanecarbonitrile.

8. A process according to claim 7, wherein the azo catalyst employed isalpha, alpha-azodiisobutyronitrile.

Example Reactants Moles Catalyst Product Number 3 Alpha dodecene tert.butyl 1:1.1 gm. azobisisobutryonitrile, n-Dodecyl tert. butyl sulfidemercaptan. 24 hrs., 60 C. 93% yield on recycle.

4 Mixture of alpha olefins con- 1:1. 1 gm. azobisisobutryonitrile, Anormal olefin tart. butyl taining from 11-15 carbons and 24 hrs., 60 C.sulfide containing from 15 to tertiary butyl mercaptan. 19 carbon atoms.

5 Mixture oi alpha olefins con- 1:15 gm. azobisisobutryonitrile, Anormal tertiary butyl sulfide taim'ng from 11-15 carbon 24 hrs., 60 0.containing from 15-19 carbon atoms and tertiary butyl atoms. 80% yieldon recycle. mereaptan.

6 Mixture of alpha olefins con- 3:3. 3 2 gms. azobisisobutryonitrlle, Anormal olefin tertiary butyl taim'ng from 11-15 carbon 33 hrs., Jsulfide containing from 15-19 atoms and tertiary butyl carbon atoms. 85%to 88% mercaptan. yield on recycle.

7 Mixture of alpha olefins con- 10:11 7.5 gms. azobisisobutryo- A normalolefin tert. butyl taining from 11-15 carbon nitrile, 53 hrs., 60 C.sulfide containing from 15-19 atoms and tertiary butyl carbon atoms.85%-88% yield mercaptan. on recycle.

8 Alpha octene and tort. butyl 10: 11 5 gins. azobisisobutryonitrile, Anormal octyl tert. butyl sulfide. rs., C. sulfide 90% yield on recycle.

9 do 10:11 5 gins. alpha,alpha-azobis(alphacyclohexopropionitrile).

10 Alpha dodecene and tart. butyl 1:1.1 HeXo-alpha(carbamylazo)-n-Dodeeyl tertiary butyl sulfide.

sulfide. alphagammardirncthyl- Greater than 90% yield.

valerate, 24 hrs., 0.

While there have been described various embodiments of the invention,the methods and elements described are not to be understood as limitingthe scope of the invention, as it is realized that changes therein arepossible by one of ordinary skill in the art.

What is claimed is:

1. A process for the preparation of an organic sulfide of the formula R2nomom-s-r'z-w which comprises reacting a compound of the formula RCH CHwith a compound of the formula R2 R J--SH b in the presence of an azocatalyst of 6 to 20 carbon atoms; wherein the substituents R, R R and Rare alkyl radicals of 1 to 20 carbon atoms.

2. A process in accordance with claim 1 wherein the olefin utilized isa-octene.

3. A process in accordance with-claim 1 wherein a mixture of olefinscontaining from 7 to 9 carbon atoms is utilized.

azobisisobutyronitrile.

10. A process for the preparation of the compound 6 13 2 2 3)3 whichcomprises reacting the compound C H CH=CH with the compound 1 (CH CSH inthe presence of azobisisobutyronitrile and at a temperature of 70degrees centigrade.

11. An integrated process for the preparation of sulfides whichcomprises reacting at a temperature of 40 degrees 5 6 oentigrade to 140degrees centigrade a compound of the References Cited formula RCH=CH2With a compound Of the formula: UNITED STATES PATENTS 2,366,453 1/ 1945Meadow 260'60 9 ilk-(FEE 5 2,543,542 2/ 1951 Badertscher et a1. 260-609a 2,610,981 9/1952 Short 260609 wherein R, R R and R are alkyl radicalsof 1 to 20 21865965 12/1958 May et a1 260 609 carbon atoms in thepresence of an azo catalyst of 6 to 20 V carbon atoms, isolating thesulfide product from the reac- CHARLES PARKER Prlmary Exammer' tionmixture and recycling the olefin and unreacted ter- 10 D. PHILLIPS,Assistant Examiner.

tiary mercaptan.

1. A PROCESS FOR THE PREPARATION OF AN ORGANIC SULFIDE OF THE FORMULA